/* utf.js - UTF-8 <=> UTF-16 convertion
 *
 * Copyright (C) 1999 Masanao Izumo <iz@onicos.co.jp> & 2006 Ma Bingyao <andot@ujn.edu.cn>
 * Version: 1.1
 * LastModified: Feb 17 2006
 * This library is free.  You can redistribute it and/or modify it.
 */

/*
 * Interfaces:
 * utf8 = utf16to8(utf16);
 * utf16 = utf16to8(utf8);
 */

function utf16to8(str) {
    var out, i, len, c;

    out = [];
    len = str.length;
    for(i = 0; i < len; i++) {
        c = str.charCodeAt(i);
        if ((c >= 0x0001) && (c <= 0x007F)) {
            out[i] = str.charAt(i);
        } else if (c > 0x07FF) {
            out[i] = String.fromCharCode(0xE0 | ((c >> 12) & 0x0F),
                                         0x80 | ((c >>  6) & 0x3F),
                                         0x80 | ((c >>  0) & 0x3F));
        } else {
            out[i] = String.fromCharCode(0xC0 | ((c >>  6) & 0x1F),
                                         0x80 | ((c >>  0) & 0x3F));
        }
    }
    return out.join('');
}

function utf8to16(str) {
    var out, i, len, c;
    var char2, char3;

    out = [];
    len = str.length;
    i = 0;
    while(i < len) {
        c = str.charCodeAt(i++);
        switch(c >> 4)
        { 
            case 0: case 1: case 2: case 3: case 4: case 5: case 6: case 7:
            // 0xxxxxxx
            out[out.length] = str.charAt(i-1);
            break;
            case 12: case 13:
            // 110x xxxx   10xx xxxx
            char2 = str.charCodeAt(i++);
            out[out.length] = String.fromCharCode(((c & 0x1F) << 6) | (char2 & 0x3F));
            break;
            case 14:
            // 1110 xxxx  10xx xxxx  10xx xxxx
            char2 = str.charCodeAt(i++);
            char3 = str.charCodeAt(i++);
            out[out.length] = String.fromCharCode(((c & 0x0F) << 12) |
                ((char2 & 0x3F) << 6) | ((char3 & 0x3F) << 0));
            break;
        }
    }

    return out.join('');
}